Our objective is to evaluate the thermodynamic properties of reactions between gaseous ligands and abnormal or unusual hemoglobins. These properties include changes of enthalpy, entropy, free energy, heat capacity, Bohr protons, and allosteric effector molecules upon ligation. Direct calorimetric measurements using a gas microcalorimeter are contemplated for the reaction between CO and Hb M Iwate in its fully reduced state over a pH range of 5.5 to 9.0 in the presence and absence of inosotyl hexaphosphate (IHP). Comparable results have been obtained on Hb A. Calorimetric measurements of ligand binding as a function of extent of reaction will be continued for Trout Hb IV as a comparative study to results obtained on Trout Hb I. We also plan to examine the oxygen binding curve of Hb S in our thin layer spectral cell to determine effects of aggregation. We plan to finish construction of a small sample (0.5 ml) gas microcalorimeter.